From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
---|---|
To: | Jan Wieck <JanWieck(at)Yahoo(dot)com> |
Cc: | Wei Weng <wweng(at)kencast(dot)com>, pgsql-sql(at)postgresql(dot)org |
Subject: | Re: Which one is faster? |
Date: | 2002-06-20 16:10:48 |
Message-ID: | 200206201610.g5KGAm507411@candle.pha.pa.us |
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Lists: | pgsql-sql |
Jan Wieck wrote:
> Bruce Momjian wrote:
> >
> > Wei Weng wrote:
> > > Between Using Limit P, S or using a cursor to start from FETCH ABSOLUTE
> > > S and FETCH NEXT for P times, which one is faster?
> >
> > LIMIT is faster because it doesn't need to generate all the result, in
> > some cases.
>
> Neither does using a cursor need to generate all the results first. It's
> a portal, which is an executor state on hold, and FETCH is implemented
> as ExecutorRun() with the number of wanted result rows as limitation.
> Since LIMIT generates internally one more result row than really wanted,
> I don't think LIMIT would be much faster, but it's for sure less
> portable.
Oh, I thought the portal had to be materialized before returning a row.
Thanks.
--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
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